The present application relates to a semiconductor structure and a method of forming the same. More particularly, the present application relates to a semiconductor structure including a multi-level interconnect structure that provides increased mechanical strength, improved anchoring and/or lower contact resistance and a method of forming such a semiconductor structure.
Multiple interconnect levels have been designed at the 7 nm node to provide wiring flexibility for system-on-chip (SOC) applications. Aggressive dimensional scaling for the 7 nm node has resulted in a significant increase in interconnect resistance. While tungsten has been used for many generations as a contact metal, it is no longer competitive because of the difficulty in scaling the thick high resistivity liner/barrier films and defectivity concerns.
Due to its ability to reflow, cobalt (Co) is attractive for void free gap fill and Co also enables scaling of the liner/barrier films. However, the reliability of Co interconnects and other low resistivity metals and metal alloy containing interconnects is a still a concern.
Similar to copper (Cu) metallization in back-end-of-the-line (BEOL) interconnects, poor mechanical strength may present challenges in terms of stress migration and electromigration for Co and other low resistivity metal or metal alloy containing interconnect structures. Therefore, there exists a need to provide reliable interconnect structures that have increased mechanical strength, improved anchoring and/or lower contact resistance.